NEW ORLEANS — Dan Quayle, the handsome, blond junior senator from Indiana who was chosen as George Bush's running mate on Tuesday, is the first member of the post-World War II baby boom generation ever to be selected for nomination to a national office.

At age 41, he is an energetic and affable conservative who specializes in defense and health issues, the grandson of the late conservative newspaper publisher Eugene Pulliam and the father of three young children. His wife, Marilyn, has a law degree.

But Quayle is barely known on the national scene. And perhaps the best known aspects of his public personality are his red-cheeked baby face, his sandy blond hair and his blue eyes--a boyish handsomeness that has proven appealing to some women voters.

Party analysts believe Quayle's enormous popularity among Indiana women can be duplicated on a national scale, helping Bush to close the so-called "gender gap" that makes him less popular with women than Democratic nominee Michael S. Dukakis. Likewise, his expertise on military affairs is expected to be popular with young males who view Bush as unassertive.

In that sense, Bush's choice of Quayle is similar to that of Democratic nominee Walter F. Mondale's selection of Geraldine A. Ferraro in 1984 because it is designed to broaden the ticket's general demographic appeal. "It is a bold choice--a strictly demographic choice," said GOP political consultant Mark Helmke, a long-time friend of Quayle.

Republicans hope Quayle will compare favorably to Dukakis' choice of a 67-year-old Texas senator as his running mate. "I can't wait to see the comparison between Lloyd Bensten and Dan Quayle--the old and the new, the past and the future," said Sen. James A. McClure (R-Ida.).

Like Bush, however, Quayle comes from a well-heeled family, which may limit the ticket's appeal to working class voters. And his life of privilege, according to one acquaintance, has made him "something of a brat."

"I've been very fortunate in my young life . . . ," Quayle told an interviewer when he was 33 years old. "There was never anything where 'I've got to work really hard to get there.' "

His conservative credentials are impeccable. "He makes Genghis Khan look like a misunderstood liberal," said a Senate Democratic aide, who refused to be named.

Born James Danforth Quayle on Feb. 4, 1947--less than two years after the end of World War II--he was graduated in 1969 from DePauw University in Greencastle, Ind., a small liberal arts college that is loosely affiliated with the Methodist Church. He was a third-generation member of his fraternity, Delta Kappa Epsilon, and met his wife in college. In 1974, he received a law degree from Indiana University Law School.

While in law school, Quayle held posts in the Indiana attorney general's office, the governor's office and the state revenue department. He then returned to his hometown and took over as associate editor of the Huntington, Ind., Herald Press, which--like the larger Indianapolis Star and the Arizona Republic--is owned by his mother's powerful family.

Start of Career

Quayle's entry into politics in 1976 as a candidate for Congress was marred by bad timing, according to Ft. Wayne Mayor Paul Helmke. "In the middle of his news conference announcing his candidacy), there was a shooting in town and all the news media pulled their plugs and ran out," Helmke recalled. "And he's still standing there. That was the start of his political career."

But Quayle defeated incumbent Rep. J. Edward Roush and served two terms in the House, accentuated by frequent absences from Capitol Hill. The Indiana press once reported that Quayle had missed 40 out of 61 sessions of the House Foreign Affairs Committee over a 14-month period.

In February, 1980, Jack Anderson wrote that Quayle's campaign organization had filmed him busily entering and leaving a meeting of the House Small Business Committee. But a half-hour later when the committee convened, the Indiana congressman was absent.

It was near the end of his four-year House tenure that Quayle went to Florida on a golf weekend with several other members--an outing that later became part of a Justice Department probe into allegations that members of Congress exchanged votes for sexual favors from lobbyist Paula Parkinson, who had posed nude in Playboy magazine.

Tells Investigators

Parkinson told investigators that the trip was just one event in a love affair with Rep. Tom Evans (R-Del.). Both Quayle and Rep. Tom Railsback (R-Ill.), who also shared the vacation house that weekend, insisted they had had no sexual relations with Parkinson.